Taste or aroma of coffee beans can be developed from coffee beans by roasting the coffee beans and the taste or aroma of coffee beans varies depending upon a roasting level. Therefore, in order to develop desired taste or aroma from coffee beans, it is necessary to produce coffee beans roasted to a desired roasting level.
As a method for producing coffee beans roasted to a desired roasting level, for instance, a method is known wherein an operator judges the state of roasting of coffee beans by performing operations including frequent check of color of coffee beans, color and amount of discharged smoke, aroma of smoke and ambient temperature in a roasting drum, etc. during roasting or listening to crack sounds generated by coffee beans undergoing roasting; and the operator operates a roasting machine so that the coffee beans are roasted to a desired roasting level.
In addition, Patent Document 1 discloses a coffee bean roaster comprising a roasting temperature sensor for detecting a roasting temperature of raw beans in a roasting drum or an exhaust temperature sensor for detecting a temperature of exhaust discharged from the roasting drum.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2003-265154